1. Field of the Invention
This invention relates to a pneumatic tire having an improved steering stability and a method of producing such a pneumatic tire, and more particularly to a front tire and a rear tire for a motorcycle and a method of producing the same.
2. Description of Related Art
In the conventional front and rear tires as a tire for a motorcycle or the like, a spiral belt formed by spirally winding a cord(s) on an outer circumference of a carcass is recently used as a belt structure. In this case, the belt is constructed by one kind of the cord. In general, there are known a spiral belt comprised of only a steel cord, a spiral belt comprised of only a reinforcing fiber cord made of a resin material or the like.
In the spiral belt comprised of only the steel cord, the rigidity becomes too high and hence it is difficult to highly maintain the ride comfort and the slip resistance. For this end, it is attempted to reduce an end count as the winding number of the steel cord for providing an appropriate rigidity.
When the end count is merely reduced in the spiral belt comprised of only the steel cord, however, there are caused troubles such as lowering of breaking strength to air pressure, lowering of puncture resistance, lowering of fatigue resistances of the tread rubber and the carcass ply against repetitive bending due to the lowering of bending rigidity in a section direction
In the spiral belt comprised of only the reinforcing fiber cord, the rigidity is lacking and an amplitude of shimmy behavior becomes easily large and hence it is difficult to maintain the high-speed stability at a higher level during the high-speed running and hold the light feeling and responsibility of the handling and maintain the gripping force at a higher level during the cornering and as a result, it is feared that the steering stability can not sufficiently be ensured.
In the spiral belt comprised of only the fiber reinforcing cord, it is attempted to increase the end count by laminating the cord or to add the other member in order to prevent the lowering of the steering stability. However, when the end count is increased more than necessary or the other members are added, it is difficult to reduce the tire weight and also the gripping force lowers due to the lowering of shearing rigidity accompanied with the lamination.